Refill fuse plug



May 31, 1938. J, CREE ET AL 2,119,269

REFILL FUSE PLUG Filed July l5, 1936 ATTORNEYS Patented May 31, 1938UNITED STATES PATENT OFFICE REFILL FUSE PLUG Application July 13,

2 Claims.

Our invention relates to improvements in fuse plugs for use inelectrical circuits and the primary objective sought is the provision ofan inexpensive, durable plug of this character of few parts which may bereadily disassembled and the fuse element thereof easily and quicklyreplaced.

Another object is to provide a plug of the character and for the purposeabove'set forth provided with a sight glass protected by a replaceableelement against being burnt, and thereby clouded, when the fuse elementis burnt or blown out whereby the plug may be kept in a condition inwhich the interior thereof is visible through said sight glass.

To the accomplishment of the above, and subordinate objects presentlyappearing, a preferred embodiment of our invention has been illustratedin the accompanying drawing, set forth in detail in the followingdescription, and defined in the claims appended hereto.

In said drawing:-

Figure 1 is a view in end elevation of our improved fuse plug looking atthe outer end thereof.

Figure 2 is a view in side elevation.

Figure 3 is a view in longitudinal section taken on the line 3-3 ofFigure 2, looking in the direction indicated by the arrows.

Figure 4 is a View in side elevation of the body part of the fuse plug.

Figure 5 is a similar view of a capsule adapted to be tted in the bodypart.

Figure 6 is a view in end elevation of the inner end of the capsule,and,

Figure 7 is a view in plan of the fuse element.

Referring to the drawing by numerals, the plug of our invention in itsillustrated embodiment, comprises a sleeve-like cylindrical body part I,preferably of glass, and including an exteriorly threaded shank part 2,a flanged outer end 3, and a cylindrical bore 4.

The outer end 3 is formed with a raised, thin, central portion 5providing a sight glass 6 through which the interior of the body part isvisible. On its inside the head is formed with an outwardly flaringcentral socket 'I directly behind the sight glass 6 in which a mica disc8 is fitted with a press fit for the purpose of protecting the sightglass 6 against becoming smoked and blurred when the fuse element,presently described, is burnt or blown out.

Fitted into the bore 4, from the inner end thereof is a substantiallycylindrical sleeve-like capsule 9 having a radial iiange I0 intermediateits ends adapted to fit against the inner end of the shank part 2, atapered outer end II extending out- 1936, Serial No. 90,404

(Cl. 20G-130) wardly of said flange I0, a flat side I2 extending fromthe flange I0 toward the inner end of the capsule and terminating at theinner edge of the latter in a squared aperture I3, and a slot I4extending from the inner end of the capsule 9 to a. point adjacent toange II) and diametrieally opposed to the recess I3. The purpose of therecess I3 and the slot I4 will presently be explained.

The capsule 9 is formed of glass or other suitable insulating materialand is secured in the bore 4 by means of a threaded shell I5 of brass orother conducting material, and having an apertured end I6 tting over theend I I of the capsule 9 and bearing against flange IIB. The shell I5 isthreaded onto the shank part 2 and retained` thereon against turning bypressing the edge thereof into a kerf II provided in the shank part 2.The capsule 9 1s locked to the shank part 2 against relative turningmovement by means of a squared boss I0 on the shank side of the flangeI0, aligned with the flat side I2 and fitting into a correspondinglyshaped recess 2 formed in the inner end of the shank part 2.

A contact post I8 is fitted into a counter bore I9 in the capsule 9,said post having a disc-like outer contact part 20 fitting against theouter end of the capsule 9 and being split longitudinally to provide apart 2|, for interlocking engagement with the capsule 9 to anchor thepost in the latter, and a fuse carrying part 22 having a squared end 23extending into said capsule along side the slot I4 in the latter for apurpose presently clear. The interlocking engagement between the post I8and the capsule 9 is effected by bending the part 2| over against acurved ledge 23 provided at the inner end of said counter bore I9.

The fuse element 24 comprises a strip of flexible conducting material ofany suitable character having inwardly extending slots 25 and 26 in itsopposite ends, respectively, and an intermediate portion 2'I of reducedwidth. The fuse element 24 is secured at one end to the square part 23of the post I8, bent at right angles to extend across the inside of thecapsule 9, through the recess I3, and downwardly along side the flatside I2 of said capsule. The other end of the fuse strip 24 is insertedthrough a slot 28 in the boss IIJ' and flange I0 and is turned outwardlyagainst the outside of said flange as shown in Figure 3. The firstmentioned end of said element 24 is secured to the squared part 23 bymeans of a screw 28 passing through the slot 2S in said end of theelement. The other end of said element 24 is secured to the fiange I0 bymeans of a squared key block 29 seating in a correspondingly shapedrecess 30 formed in the outer side of said flange I0 and boss I0 and towhich block said end of the element 24 is secured by means of a screw3I. The head of the screw 3| engages the shell I5 to establish a circuitthrough the post I 8, element 24 and said shell I5. The reduced portion2l of the fuse element 24, as will be understood, provides a weakenedportion in said element to be burnt or blown out in the event of anover-load in the circuit. The arrangement of the fuse element 24 is suchthat the weakened portion 21 is parallel with the sight glass 6 andthereby plainly visible through the latter.

By forcibly unscrewing the shell I5 and forcing the detent therein outof the kerf I'I, the capsule 9 together with the fuse element 24 may beeasily and quickly removed from the body part I of the plug and the keyblock 29 and corresponding end of the element 24 detached from theflange IQ. The screws 28 and 3l may then be removed and the burnt orblown out fuse replaced. The slot I4 in the capsule 9 facilitates theinsertion of a screw driver against the screw 28 and the latter in thepost and provides for visibility in positioning the slotted end of thefuse element over said screw. The recess i3, flat side I2, and key block29 provide a simple arrange` ment of parts functioning in conjunctionwith the bore 4 to securely hold the fuse element 24 in proper position.When the mica disc 8 becomes smoked, or otherwise clouded, it may bereadily pried out of the socket l and replaced with a new one.

The foregoing description will, it is believed, suffice to impart aclear understanding of our invention together with the advantagesthereof.

It is to be understood that the present disclosure is illustrative ofpreferred embodiment of our invention, only, and that right is hereinreserved to modications in details described falling within the scope ofthe appended claims.

What we claim iszl. In a fuse plug, a cylindrical sleeve-like body partof insulating material exteriorly threaded,

a cylindrical sleeve-like capsule fitted into said part and including anintermediate radial flange adapted to seat against one end of said partand a flat outer side extending from said flange toward the inner end ofthe capsule and terminating in a recess in said end of the latter, acylindrical cup-like shell of conducting material threaded onto saidpart and iitting over said capsule against said ange to retain thecapsule in the body part, a contact post extending into said capsulefrom one end thereof, and means for detachably securing said other endto said flange comprising a squared key block, said ilange having acorrespondingly shaped recess therein receiving said block.

2. In a fuse plug, a cylindrical sleeve-like body part of insulatingmaterial exteriorly threaded, a cylindrical sleeve-like capsule fittedinto said part .and including an intermediate radial flange adapted toseat against one end of said part, and g a flat outer side extendingfrom said flange to ward the inner end of the capsule and terminat ingin the recess in said end of the latter, said capsule having alongitudinally extending slot therein opposite said recess, acylindrical cupn like shell of conducting material threaded onto saidbody part and fitting over said capsule against said flange to retainthe capsule in said part, a contact post extending into said capsulealong side said slot, a strip-like fuse element having slotted ends andextending from said post across said capsule through the recess thereinand along side said at face and through said iiange, a screw passingthrough the slot in one end of said Velement to secure the latter to thepost, the I key block, and a screw passing through. the slot and intosaid block said flange having a recess therein receiving said block.

JOHN CREE. FRANK CORLETT.

